Listen.
I'm adopted, but I was taken from my birth mother due to abuse. So I can see where this kid is coming from. You can say they raised him, ect ect. But I guarantee he has never felt the bond he has felt with his birth parents, as he does now. That shyt is a daily process of what ifs, and questions. He feels hurt, lied to and let down. And it's probably overwhelming to him, wishing he had that bond all his life. But yes, he is acting a little over board and disrespectful. I'm sure it will all blow over, and everything will balance out.